Dating of igneous and metamorphic events in the Fiskenaesset region of southern west Greenland

Abstract

U–Pb measurements on zircons from gneisses, which closely resemble Amitsoq gneisses, from nunataks from the Frederikshåbs Isblink show that they are in fact much younger, probably ca. 3000 Ma old. A direct measurement of the age of the granulite facies metamorphism in the northern part of the Fiskenaesset area, of [Formula: see text], has been achieved by U–Pb analyses on: (1) a large euhedral zircon from an ultrabasic pod considered to have crystallized during the granulite facies metamorphism; (2) zircons from the Ilivertalik granite, which is considered to have been emplaced shortly before the end of the granulite facies metamorphism; and (3) zircons from an anthophyllite–gedrite rock considered to have grown during the amphibolite facies retrogression following granulite facies metamorphism.A maximum age of 2660 ± 20 Ma for the end of the low grade amphibolite facies overprinting in the southern part of the Fiskenaesset area is given by a zircon U–Pb measurement on intrusive granitic sheets.